Microsoft Corp is talking to Facebook about buying a minority stake in the fast-growing online social network that could value the company at $10 billion or more, the Wall Street Journal reported on its Web site on Monday.

Citing people familiar with the matter, the Journal said the world's largest software company sought to buy a stake of up to 5 percent in Facebook for $300 million to $500 million.

Facebook, led by its 23-year-old founder and Chief Executive Mark Zuckerberg, may insist on a valuation as high as $15 billion and is considering raising up to $500 million in cash to expand its operations, according to the Journal.

Such a deal could help Microsoft better compete against Web search leader Google Inc for a growing base of online advertising and put one of the Internet's hottest names firmly in Microsoft's camp.

Google has also expressed an interest in investing in Facebook, the Journal report said.

It would probably be pretty good for Microsoft since it has not had the best success in creating really hip, young-people-grabbing stuff on the Web, said Kim Caughey, a senior analyst at Fort Pitt Capital Group, which oversees more than $1 billion, including Microsoft shares, for clients.

Microsoft would not comment on the report, while Facebook representatives were not immediately available to comment.

Facebook, which allows members to seek out a circle of friends and share online activities, has seen speculation over a potential partnership or buyout intensify as it rapidly expands its base of users and advertisers.

It has grown to 39 million members, up nearly 63 percent from 24 million in late May, and is quickly gaining ground against larger rival MySpace, bought by News Corp in 2005 for what is now seen as a bargain price of $580 million. MySpace now has more than 200 million users.

Redmond, Washington-based Microsoft already has an exclusive agreement until 2011 to broker display advertisements for Facebook. The Journal said Microsoft and Facebook are discussing expanding that agreement beyond the United States.

After relinquishing an early advantage in the lucrative paid search market to Google and Yahoo Inc, Microsoft is trying to catch up by clinching deals to broker display advertising to some of the leading names in Web 2.0.

Web 2.0 is a catch-phrase for a new generation of Internet services that run on interactive software and typically rely on content generated by users to attract more visitors to the site. Microsoft also has an agreement with popular news site

Microsoft shares rose 1.5 percent to $29.08 in late trading on the Nasdaq. The stock was off its Monday high of $29.61.